While the flywheel is off is a good time to inspect the ring gear for wear. You can see one--maybe--two areas where the starter drive gear has been engaging the ring gear. If those areas are worn much at all, at some point, it will start grinding when the starter is engaged. Heat the ring gear, then tap off by going all around with a piece of wood under your hammer. Rotate the gear about 90 degrees and tap back on while it is quite warm.
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